Description: (Applicant's Description) The Transgenic Mouse Shared Resource provides five services related to the production and maintenance of transgenic and knock-out mouse lines. These include: 1) The production of new lines of transgenic mice for SACI members. Investigators provide the core with a plasmid containing the desired transgene and a detailed plasmid map. The core is responsible for isolation of the transgene fragment and the production and identification of transgenic founder mice. At least two founder mice are produced for each transgene. 2) Mouse line rederivation by embryo transfer to eliminate pathogens from mice which have been obtained from outside, non-commercial sources. This method is highly effective and greatly reduces the cost and time involved in the quarantine approach to pathogen elimination. 3) Mouse lime embryo cryopreservation. This approach provides the means to preserve lines of mice without active breeding as well as safeguarding against the loss of mouse lines due to disease. 4) Blastocyst injection of embryonic stem (ES) cells for the production of knock-out mouse lines. This represents a new service to be added to the Transgenic Mouse Shared Resource Investigators provide the core with ES cell lines in which a specific gene has been disrupted by a homologous recombination. The core microinjects these cells into mouse blastocysts to produce chimeric mice. The core will also coordinate with a developing ES and feeder cell lines, targeting vectors, protocols and advice on ES cell culturing and manipulation. 5) Consulting services. The core staff provides advice on general transgenic and knock-out approaches and plasmid construction. For laboratories lacking experience with transgenic mice, instruction is provided on breeding of mice, weaning, ear punching, and tail DNA isolation. The core also provides assistance in preparing applications to the UTHSCSA IACUC for the use of laboratory animals in research.